Airships are lighter than air flying vehicles which are also called dirigibles. Modern airships have a rigid framework which carry lifting bladders that are filled with a lighter than air substance, such as helium. The use of sufficient helium will make the entire structure "lighter than air" allowing it to rise into the air. The amount of rise and or descent is controllable through various systems that are well known in the art.
Modern airships include a passenger and crew gondola attached to the underside of the airship. This gondola is typically small and has limited capacity for carrying passengers. Propulsion is provided by one or more engines or motors powering fans or propellers. Accordingly, fuel for such engines or motors must be carried on the airship, further limiting its ability to carry passengers and/or cargo.
The passenger gondolas used on airships today are enclosed compartments in which the passengers and crew are carried. Because the gondola is carried beneath the airship, there is no exposed deck, akin to the deck of a sailing ship, on which the passengers might be carried. Thus, traveling in a modern airship is a somewhat confining experience. The sense of freedom one receives on the deck of a sailing ship, or from the unenclosed confines of a basket of a hot air balloon, are missing from the gondolas used on airships.
Airships are designed to operate in portions of the lower atmosphere where significant winds are often present. Yet, modern airships do not attempt to use such winds for propulsion. In fact, the elongated, oval shape of most modern airships preclude any effective use of the wind for propulsion. Accordingly, propulsion is exclusively provided by the engines or motors carried on the airship.
Various patents directed to airships have suggested using wind catching sails for helping to propel the airship. See U.S. Pat. No. 827,157 to Kramer, U.S. Pat. No. 922,549 to Wheeler, U.S. Pat. No. 1,023,404 to Wymore, U.S. Pat. No. 1,045,337 to Spilka and U.S. Pat. No. 1,061,484 to Lowe. However, in such patents, the sails are generally beneath the lifting bladders or gas envelope of the airship, limiting sail size and thus effectiveness. In Spilka, the sail is shown above the lifting bladders but far removed from the passenger and crew carrying structure of the airship. Thus, it would be difficult to deploy the sail and adjust its orientation relative to the prevailing winds.
Moreover, all of the sails shown in the above noted patents teach a fixed sail carrying mast like that used on boats or sailing ships. In other words, the mast is fixed during use to the framework of the airship with the bottom of the sail pivoting around the mast on a pivotal, substantially horizontal boom. The sail is locked in place by cinching or securing the boom in place. However, this structure does not maximize the sail area and limits the adjustability of the sails relative to the prevailing winds.